A well known method for magnetic recording on a magnetic medium resorts to localized irradiation of light on a region of the magnetic recording medium placed in a magnetic field to thereby provide heat energy which changes the magnetic state of the region. This method has been known to provide high density recording.
However, most of the materials for use in such magneto-optical recording as mentioned above are ferromagnetic, so that, due to their internal magnetic effect, magnetic spins are oriented in the direction parallel to the surface of the medium, resulting in a recording density much less than the recording density that would be obtained by perpendicular recording.
Another disadvantage of such prior art is that multiple recording is not possible since the magnetization of the medium is dichotomic, i.e. it has only two magnetic states, corresponding to digital states 1 and 0. Further, it is necessary to use a high-power laser in the prior art recording/erasing to heat the medium, since the medium must be heated above the Curie temperature.
The only existing material available for so-called perpendicular magnetization for use in magneto-optical recording is TbFeCo alloy. The alloy is, however, not only expensive but also very susceptible to external magnetic fields and oxidation.